This invention relates generally to a hollow-fiber permeability apparatus, and more particularly to a hollow-fiber permeability apparatus in which a permeating region of a housing contains a bundle of hollow fibers, and materials can selectively permeate through the membances formed by the permeable walls of the hollow fibers, between a fluid flowing along the exteriors of the hollow fibers, and another fluid flowing the interiors of the hollow fibers. The permeation may be based on the principles of osmosis, dialysis, ultrafiltration, reverse osmosis or the like.
2. Description of the Prior Art
For example, a conventional hollow-fiber permeability apparatus (dialyzer) is used for blood dialysis, in which toxic materials are removed from the blood of a patient suffering from renal failure or medicinal poisoning.
The hollow fibers used in the blood dialyzer provide a relatively large effective surface area of membrane for the size. Therefore, the dialyzer can be smaller than conventional coil-type or Kiil-type dialyzer. Thus, the blood priming volume of hollow fiber dialyzer can be smaller, which is beneficial to the patient during dialysis. The apparatus is also easier to handle, and the hollow fibres are strong for pressure change, therefore the hollow fibers are advantageous for ultrafiltration.
Since the hollow fiber dialyzer has many advantages it has become popular recently. However, the dialyzer has the following disadvantages.
As shown in FIG. 1 ten to fifteen thousand hollow fibers 5 are closely bundled in the permeating region 25 of the cylindrical housing 1 of the dialyzer 10. It is difficult that the dialysate 35 can perfuse uniformly through the whole part of the bundle 6. It is experimentally proved that the dialysate flows mainly around the peripheral region of the bundle 6 adjacent to the inner wall of the housing 1, and the dialysis performance is extremely low in the central region of the bundle 6.
In order to remove the above described disadvantages, for example, the hollow fiber dialyzer 10 shown in FIG. 2 was already proposed in U.S. Pat. Appln. Ser. No. 653,351. In the apparatus 10 of FIG. 2, the crosswise cross-section of the housing 1 is flat and generally oblong with round short sides. The housing 1 has, as a whole, point symmetrical contiguration. Enlarged cross-section portions 16 and 17 which are trapezoid in cross-section, are formed in the opposite longer sides of the housing 1 to which the inlet and outlet tubes are connected, respectively.
As the results of the progress of the study, the inventors have found that, in the blood dialyzer 10 having the oblong cross section, the thickness of the hollow fiber bundle 6, packing wet-density of hollow fibers, and the shapes of the enlarged cross-section portion connected to the dialysate inlet and outlet having great influences on the dialysate flow 35 in the housing 1 and hence on the performance of the dialyzer.